Abnormalities in lipid metabolism are a recognized side effect of protease inhibitor (PI) therapy in HIV-infected patients. EFV also is known to increase plasma cholesterol. In an attempt to normalize serum lipids in HIV-infected patients on PIs and/or EFV, Hydroxymethylglutaryl Coenzyme A (HMG-CoA) reductase inhibitors (also known as statins) may be prescribed. Therefore, it is important to study how PIs and EFV affect the PK of concurrently-administered statins. Many of the statins utilize the cytochrome P450 (CYP) 3A4 enzyme for metabolism. In addition, atorvastatin and simvastatin have active metabolites, generated via CYP3A4, that contribute to the drugs' lipid-lowering activity and probably to their toxicity. Pravastatin is not metabolized by CYP3A4 but is inactivated by conjugation, non-CYP3A4-induced hydroxylation, and renal excretion. NFV, the most commonly used PI, is an inhibitor of CYP3A4 and an inducer of other CYPs and conjugative pathways. EFV is a mixed CYP3A4 inhibitor and inducer. This study examines the effect of NFV on the PK of pravastatin and the effect of EFV on the PK of simvastatin, atorvastatin, and pravastatin. As EFV with pravastatin is expected to be a common drug combination during the treatment of HIV infection, it should be explored further, even though drug interactions are not expected. To expedite this study, the study population is comprised of healthy control volunteers.